Finished sheet material and method of finishing the same



L. M. PERRY Sept. 16 1924.

FINISHED SHEET MATERIAL AND METHOD OF FINISHING THE SAME Filed July 1, 1922 lmavemEwr dMPwr Patented Sept. lfi, ieae.

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LLOYD M. PERRY, F NASHUA, NEW HAMPSHIRE, ASSIGNOR T0 NASHUA GUMMED & COATED PAPER COMPANY, OF NASHUA, NEW HAMPSHIRE, A CORPORATION OF MASSACHUSETTS.

FINISHED SHEET MATERIAL AND METHOD 0] FINISHING THE SAME.

Application filed July 1,

To all whom it may concern:

Be it known that I, LLOYD M. PERRY, a citizen of the United States, and a resident of Nashua, in the county of Hillsborough 6 and State of New Hampshire, have invented an Improvement in Finished Sheet Material and Methods of Finishing the Same, of which the following description, in connection with the accompanying drawings, is a 10 specification, like characters on the drawings representing like parts.

The object of this invention is to provide an improved method of surface-finishing paper or other sheet material and an improved product which avoids certain disadvantages inherent in the processes heretofore employed.

The common method of producing a glazed finish surface on paper has been first to cover the paper with a surfacecoating containing a wax emulsion, the latter belng prepared from carnauba wax, beeswax, ceresine or other wax or oil capable of emulsification when heated with dilute alkaline solution or with alkaline solution and soap. In the case of coated paper this emulsion is mixed with the coating compound and applied to the surface of the paper. After being dried it is passed through a friction calender and subjected tonthe burnishing action of the calender re s.

It is diificult, however, completely to emulsify thewax or completely to maintain it emulsified. Relatively large particles of free wax are apt to be present causing streaks or spots on the-paper under the action of the friction calender. The alkali A required to insure emulsification of the wax 46 is also apt to afiect the shades in certain dyes and pigments. These and other dificulties I have found can be avoided by using as a substitute for the wax emulsion an insoluble metallic salt of a fatty acid,

such as zinc stearate. I

The invention willbe best understood by reference to the following description when taken in connection with the accompanying illustration showing one method of appl to hug the coatingand finishing the paper, t e

sco e of the invention being more particular y. ointed out in the appended claims.

In e drawings,-

Fig. 1 is a diagrammatic representation 1922. Serial no. 572,279.

of the apparatus commonly employed in coating sheet paper; and

Fig. 2 is a diagrammatic representation of a calender machine for imparting a surface finish to the paper after it has been coated by. my improved process.

In carrying out my invention I employ a certain amount of an insoluble metallic salt of a fatty acid, such as zinc stearate. The latter can be obtained in either dry, or in pulp form having approximately 7 5% water.

Zinc stearate in dry form is diflicult to incorporate with the coating compound, and prior to such incorporation must be made into a smooth paste with water; preferably to the paste thus formed, there is added a certain amount of sulphonated oil, such as Turkey red oil, in the approximate proportion of three pints of oil to thirty pounds of dry zinc stearate. This produces a paste of smoother consistency.

Zinc stearate in pulp form is more easily incorporated with the coating mixture, but

more or less water is apt to evaporate from the pulp form during storage, so that with the dry form a coating mixture of more accurate proportions may be prepared.

The paste thus prepared "from dry zinc stearate, or the zinc stearate in pulp form (used directly) may be used very much as the wax emulsion referred to has heretofore been used, although it is necessary to add only about one-half as much (on a dry basis) of the zinc stearate as in the case of the wax emulsion.

In preparing the coating, the coating mixture is first mixed as heretofore. The zinc stearate paste, prepared as described, is then added to the coating mixture and mixed thoroughly in an ordinary mixing machine.

The amount of zinc stearat'e to be added to the coating mixture should referably be about 1% to 3% (on a dry asis) of zinc stearate in the total coating mixture, dependent on the nature of the coating with which it is used. When the color mix has had the zinc stearate thoroughly intermingled, there should be added to the completed mixture a quantity of some suitable sizing, such as casein. The quantity will vary with the nature of the coating but ordinarily will be approximately from 10 to 12%. The amount of water in the color mix will vary with the it may pigment used. When the coating is thus finally prepared the zinc steara'te or other salt employed is in a finely divided solid form thoroughly incorporated in the color mix.

7 and the paper sheet 17. The coating thus" applied to the paper sheet is smoothed and distributed by any suitable means, as by means of the stationary brush 19, engaging .the paper while still on the cylinder, and a series of brushes 21 which may be either stationary or movable engaging the paper sheet where it passes over the rubber apron 23. The sheet then passes to a suitable drying apparatus which is indicated conventionally onl at 25, where it is hung in festoons and subJected to the necessary drying action, whence it passes to. and is wound upon the storage drum 27. v

To-give the paper sheet its surface finish be subjected to any suitable finishing action, such as that of a friction calender, a super-calender,- a flint machine, or a brush machine. Herein for illustrative purposes, there is diagrammatically shown in Fig. 2 a friction calender having the calender rolls 29 and 31. The roll 29 may be of steel with a hard smooth surface and interiorly heated. It is adjustably pressed against the low er' roll 31, the latter having a relatively yieldable surface such as is presented by rings of compressed cotton. The cotton surfaced roll 31 is driven by frictional contact with the underlying smooth steel roll 32 at the same speed as that of the roll 32' and at a somewhat lesser speed than that of the roll 29. The paper passes from the roll 27, where it is subjected to a drag or braking action, through the calender rolls to the roll 33 on which it is wound up for storage or shipment. The coating thus applied and containing the zinc stearate responds readily to the the calender rolls and gives a high finish without certain of thedefects involved in the use of wax emulsion.

Through the use of an insoluble metallic salt of a fatty acid, such as zinc stearate, a coating substantially invariable in its composition may be applied. In the use of wax emulsions for this purpose there is not only an unavoidable variation in the quality of the wax and m the strength of the alkali,

burnishing action of but a variation due to the personalffactor' in preparing it.-- Carnaub'aiflW-ax and bees-' wax also. contain impurities, whereas zinc stear ate and all the insolublesalts of fatty acids may be obtainedfla-s f'substantially chemically pure products. f;Zi'nc,, stearate, furthermore, is very white, giving a lighter shade tothe coating and lpermittingy-al 2-.; v

brighter color to be obtained-than in the case of wax emulsions which'tend to give the paper a yellowish tinge. I The melting point.

of-zinc stearate, and of a number of otherinsoluble salts of fatty acids, is'relatively ings, where opacity is desired, the opacity of the coatlng is preserved, Whereas in the case of the waxemulsions the coating tends to become more or less transparent under the action of the friction calender. In cases where this opacity is not desired, an insoluble salt of a fatty acid having a lower melting point may be employed, such, for example, as an oleate.-or a mixture of an oleate and a stearate.

The quality of the paper finished by zinc stearate is ;.,as good or better than that finished by the best wax, while the cost of the zinc stearate is no more than that of the cheapest wax employed and about half as .much as that'of the best wax. Wax emulsions are also sensitive to impurities such asmineral salts in the color mix and the emulsions are apt to be broken down thereby, causing imperfection in the finished paper. The excess of alkali commonly res- .ent in wax emulsions also has a ten ency is a common occurrence in the use of wax emulsion, duechiefly to the presence of soap in the emulsion.

The paper coated with the use of zinc stearate also has a softer quality and lacks the harshness of paper finished through the use of wax emulsion. I

A glazed finished waterproofed paper in which the waterproofing agent is casein, shellac or other materials soluble in dilute alkali is more waterproof when made with 4 zinc stearate than when made with wax emulsion, since the latter commonly contains an excess of fixed alkali which impairs the water resistance of the waterproofing agent; whereas zinc stearate is ,free from such alkali.

The intention is particularly applicable .super-calenders and brush machines.

escapee to glazed coated paper'finished on the friction calender, but is also usable for finishing coated paper by means of flint machines,

may also be advantageously used in the surface finishing of sheet material other than paper or of paper products which'are not commonly termed coated, such, for example, as so-called high finished press-board.

While I haveherein shown and described for purposes of illustration one specific embodiment of the invention, it is to be understood that the same is not limited to the particular detailed steps or substances here in referred to, but that extensivedeviations may be made therefrom without. departing from the spirit thereof.

2. The method of surface finishing paper or the like which consists in preparing a liquid coating mixture including a pigment and zinc stearate, applying said mixture to the surface of the paper, dryin the same, and subjecting it to the burnis 'ng'action of a finishing agent to produce. a non-transferable'a'dherent glaze.

3. The method of surface finishing sheetmaterial which consists in preparing a'liquid coating mixture containing an insoluble salt of a fatty acid in finely divided solid form and capable of producing a glazed surface under a finishin action, applying said mix,- ture to the sur ace of the material, drying the same, and subjecting it to the action of a finishing agent to produce a non-transferable, closely adherent, glazed coating.

. 4. A surface coated, glazed paper having a surface coating only of a closely adherent and a permanent non-transferable glaze the latter containing an insoluble salt of a fatty acid. I

In testimony whereof, I have signed my name to this specification.

LLOYD M. PERRY. 

